Sun compass



Oct. 7, 1952 E. o. SCHONSTEDT SUN COMPASS Filed March 8, 1951 6 Sheets-Sheet l INVENTOR. E. O. SCHONSTEDT ATTYS.

Oct. 7, 1952 E. o. SCHONSTEDT 2,612,693

SUN COMPASS 5119a March 8, 1951 6 Sheeos$heet 2 FIG.8.

REDUCTION GEAR v. INVENTOR.

E O. SCHONSTEDT ATT/S.

Oct. 7, 1952 E. o. SCHONSTEDT 2,612,693

SUN COMPASS 6 Sheets-Sheet 3 Filed March 8, 1951 FICA.

INVENTOR. "E.O.SCHONSTEDT Oct. 7, 1952 E. o. SCHONSTEDT 2,612,693

SUN COMPASS Filed March 8, 1951 6 Sheets-Sheet 4 INVENTOR. E. O. SCHONSTEDT g6 ATTYS.

Oct. 7, 1952 E. o. SCHONSTEDT 2,612,693

SUN COMPASS 7 Filed March 8, 1951 6 Sheets-Sheet 5 g xxxmm INVENTOR. E. O. SCHONSTEDT RAM ATTYS.

E. o. SCHONSTEDT 2,612,693

Oct. 7, 1952 sun COMPASS Filed March 8, 1951 6 Sheets-Sheet 6,

FIG.9.

FIG.10

' INVENTOR. E. O. SCHONSTEDT Patented Oct. 7, 1.952

UNITED STATES JPATENT, OFFICE. I 2.612.693 Q I SUN COMPASS Erick 0. Schema, Washington, 11.56. Application March a, 1951, Serial No. 214,619

(or. sa -e1 (Granted under the act of March 3, 1883}. amended April.30, 1928; 370 G. 757% 2 Claims.

vector as disclosed in. my copending application for Method andApparatus for Measuring the Earths. Total Magnetic'Field Vector, Serial No.

187,653, filed September 29, 1950.

In. accordance with prior art methods of measuring. the relative bearing .of an aircraft with respect to the sun, the navigator stands with his head within the astral dome and first levels an instrument having a sighting telescope which he. adjusts until the cross hairs thereof intersect the center of the sun. In this position of adjustment the instantaneous relative bearing is indicated on a circular scale, and 'is' read and recorded by the navigator, or is communicated to an assistant whorecords the reading. The foregoingstepswiththe exception of the leveling step are repeated a sufficient number of times to obtain an average reading from which the effects of aircraft acccelerations are substantially eliminated. This prior art method has the-disadvantage that it i difilcult, if at all possible, to obtain r readings at precisely timed intervals.-

In accordance with the. arrangement of the present .invention, a transparent disk having a semiopaque upper surface is provided with a damped pendulous mounting whereby the disk is maintained in substantially horizontal position, the disk having inscribed on the semiopaque surface thereof a scalemarked in degrees of azimuth. A. rod secured to the disk .for movement therewith projects vertically and axially, above the disk,

and. is. mounted to cast a shadow acrossthe scale of thedisk when the sun compass is subjected to theisunsrays.

In accordance with the preferred embodiment.

ofthe present invention, a mirror or other. refleeting surfaceis 'adjustably mounted beneath the disk to reflectthe. image of the shadow and a porti'onof the scale adjacent thereto to the navigator'seatedbelow the. astraldome of the aircraft in which position he may conveniently operateandadding; machine torecord thereon read ing's' viewed inv the mirror. When preferably ten readings have; been recorded at predetermined 2' time sequence proportional to the period? of phugoid oscillations of the aircraft, the sum"'of the ten readings i's-obtai'ned from the addinglm'achine. This sum is" also the averagevaluej of the readings" upon proper shift of the dec'ifri'ral point.

Inv a slight modification of thepresen't mvem tion the mirror may be replaced by a camera for photographically recording" the heading and; vari'- ations thereof as ind-icated'by the movement of the shadow with respect to the disk. Such photo: graphs are taken at" predetermined intervals of time. andare averaged'tc produce a moreaccur'ate; result.

Anob'j'ect' of the present invention. is topfo vide a new and improved apparatusfor indicat ing variations in heading/with respect-.156 the suns azimuth of an aircraft in flight; I

Another object is to provide new andim'provedi apparatus for indicatingasuch variationsin'head ing and which is rugged and simple in construction.

with respect to the suns azimuth which is maintained in a substantially stable condition with respect to vertical.

A- further object is-lto provide apparatusifor indicating therelative bearing of an aircraftin flight with respect-to the suns azimuth wherein.

Other object and many of the atrenaantad vantages of thi's-inventi'on will be readily appreoi ated. as the same becomes better'und'erstood. by"

reference to the following detailed". description)- when considered in. connection with the'acc'ompanying, drawings wherein:

Figs. 1 and 2 are diagrammatic views".of .aii'...

craft having mountedtherein sun compasse'siao cording to. the preferred andlmodi-fi'ed "embo'di men-ts ofthe'inventionrespectively;

Fig. 31's asection'alview of a-portionof of .thevsuncompass or relative bearing indicator of the present invention in elevation;

sun. another object is to provideiapparatus for indicatingthe'heading of an aircraft infii'ght the. aircraft. and. showing. the preferred embodiment dome ll.

of Fig.

Fig. 8 is a schematic diagram of the modified embodiment of the present invention wherein a photographic recording is made of variations in heading;

Fig. 9 is a plan view of a local sun time chart for use with the sun compass'of the present invention;

Fig. 10 is a fragmentary sectional view of the compass and showing means carried thereby for balancing the pendulously supported system against coriolis acceleration effects; and

Fig. 11 is a sectional view taken along the line ll-ll ofFig.l0.

Referring more particularly to the drawings wherein like numerals indicate like parts throughout thewseveral views,- it] indicates an aircraft havingan astral dome H'in which the sun compass indicated generally at I2 is located.

" I ,The supportin spider indicated generally at l3 and as best seen in Fig. 5 comprises a mountingring l4 having preferably a plurality of horiz'ontal arms 15 radiating therefrom, each of the arms terminating in a socket [6. Each of the sockets 16 has extending vertically therethrough a.fstanchion or rod 11, the stanchions ll being bolted to the circular frame l8 below the astral The lower ends of stanchions I! are provided with rubber bumper pads 20 in order to prevent injury to personnel,

The stanchions I; are provided with a plurality of transverse bores l9. .A flanged ring 2| is mounted on each of the stanchions ll. Mounted in bore 22' of each ring 2| is a sliding bolt 23 having'a fiat portion 24. Pin 25, mounted in ring 2 I, extends into bore 22 and bears against flat por- 'tion-Zfl of bolt 23 for limiting movement of the bolt-23. It is, of course, understood that bolt 23,

when in looking positionsecures the ring 21 to stanchion H, in each case, by extendin through bore 22 of ring 2| and oneof the bores IQ of stanchion ll. Each of the socket ends 16 of the spider 13:1:85135 on one of the rings 2|, thus the spider maybe held in a plurality of vertically adjusted positions. I I

A cylindrical vessel 2-6 having a circumferential ring. 21 secured intermediate the top and bottom thereof and containing a quantity of oil of known viscosity is mounted for rotational adjustment in mounting ring I 4, a clamping screw 28 being threadedly mounted in ring M for locking vessel tally fixed in supports 34 and extend inwardly therefrom.

Mounted for pivotal movement on pins 36 is a gimbal ring 31. 'Ball bearing assemblies 38 are mounted in sockets 39of ring 37 to receive extensions of pins 36. Gimbal ring 31 has mounted therein and extending inwardly therefrom pins M, Fig. 4, whichare arranged at a 90 position withrespect to pins 36.

Axial member 42 of the gimbals assembly 33 has mounted in sockets 43 therein ball bearing assemblies 44 which receive the pins ll of ring 31. Member 42 is provided with an axial bore 45 having a reduced portion 36., A rod 4'1 is secured in bore 45, Fig. 7, by set screws 23. Rod d7 extends downwardly intovessel 26 and has supported.

thereon by set-screws 39, Fig. a pendulum member or plumb bob 5!.

Pendulum member 5] has an annular groove 52 formed adjacent the lower edge thereof, a ring the vertical.

53 of rubber-like material being mounted therein for the purpose of preventing contact of member 5i with the inner wall of vessel 25.

A transparent disk member 5 2 is secured ,by'a plurality of screws 55 to a smaller metallic disk member 55, while the smaller disk member is secured by screws 57, Fig. 7, to the axial member #12.

The disks 54 and 56 have axial bores 58 and 59,

respectively, formed therein. A rod 6! of small diameter passes through bores 53 and 59 and is a when the suns rays reach the sun compass at an angle approaching parallel to the surface of disk 54. Under this condition, a short rod 5!, is used and the sun compass is moved on stanchions ll well into the astral dome II in order to receive the suns rays and to prevent contact of the upper end of rod 6! with the dome ii. A condition at the opposite extreme is when the suns rays reach the sun compass at an'angle approaching Under this condition, a long rod is used in order to extend the shadow cast by rod =8! well into a chart 62 mounted on disk at;

The chart 62, Fig. 6, is formed of a s'emiopaque material such, for example,as frosted glass, tr anslucent white celluloid, or other suitable material applied to the upper surface of disk 5t and is inscribed with a scale 63 indicative of degrees of azimuth and which is visible from below disk 54. It is, of course, to be understood that the shadow, as indicated at 64, of: rod '6! extends across scale 63, the position thereof on the'scale changing as the heading and position of the aircraft varies and as time changes.

In the preferred form of the invention, a supporting ring 65 is held in adjusted position by a locking screw 66 threadedly mounted thereon and engaging the vessel '26, the ring 65 resting on ring 21. A supporting articulated arm indicated generally at 61 extends horizontally from ring 65.- Arm 6! comprises a plurality of sections 68 joined by elbow joints B9 and H. A mirror 12 is mounted on one of the sections 68 by means of a lock ing ball joint 1!]. The joints 69 have the pivoting axes thereof arranged horizontally, while the joint H has the axis thereof arranged at right angles to those of joints 69. By adjusting the angle of the joints 69, I0 and H and by rotating ring 65 around the vessel 26, a wide range of positions and angles beneath disk 54 may be selected for the mirror 12. Bolts 13 which form the axes of joints 69 and II have nuts 14 threadedly mounted thereon whereby thejoints may be set in any one of the adjusted positions thereof required to portion orthediskeflf and. scale B31 onwhich the shadow" of rod 6 I appears.

The-foregoing mirror arrangement is employed for" the reasonthat the sun compass occupies 'the interior" of the astral dome, leaving" no room mirror. '12. The camera T isemployed tomake aphotographic record of variations in heading ofthe aircraft as indicated by movement of the shadow'fi l withrespect to scale 63, photographs being; made atmeasured intervals of time during theflight of the aircraft.

The camera. 15. is provided' with an electrically:

operated shutter and film feed mechanism indicated schematically at 76. A cam and switch mechanism 1.! isprovided to energize the shutter mechanism 16 at timed intervals during the flight of the aircraft. Mechanism 1'! has provided therefor a cam 18 having a plurality of raised cam surfaces 19 whereby switch BI is closed to energize the shutter mechanism 16. A synchronousmotor 32; drives a reduction gear 83 which in. turn drives the cam. .18 at a speed. of one. revolution in 5 minutes, the surfaces!!! being spacedtoenergize the shutter mechanism to,ex posethe film contained in the camera and to move the film to a new position every 6 seconds for a periodof approximately 2 minutes of each 5 minute period. If desired the cam surfaces, 79 maybe removable for adjustment around the periphery of cam 18, thus the 2 minute period may be changed" with respect. to. the 5 minute period. v

An average. of the photographic valuesover the 2 minute interval is taken so as to eliminate the. effects of aircraft accelerations on the accuracy of the measurements it being recalled that the compass assembly is pendulously supported and therefore is susceptible to angular displacement in response to accelerations of the aircraft. The average of the values is representative of the aircraft relative bearing for the midpoint of the interval. A two-minute interval is employed here but this interval may be varied to suit the.

aircraft flight characteristics.

In computing true heading of the aircraft, the navigators watchis set for Greenwich sun time which is Greenwich mean time plus or minus the correction for equation of time, such correction being given on the azimuth computer disclosed in Patent No. 2,408,776 issued to Joseph Hilsenrath and Samuel Globe. The position of the aircraft with respect to latitude and longitude being known, the local sun time can be determined by correlating the instant position of the aircraft with Greenwich sun time. By employing local sun time, latitude, and day of the year, the suns azimuth can be computed by using the aforementioned azimuth computer. By employing the reading of the suns azimuth as thus obtained from the azimuth computer and the reading of the sun compass as obtained from scale 63, true heading may be computed, as will appear more 6; been provided a, local suntime chartshown in- Fig. 9. Chart 86 comprises a .disl'r-inerrb, ber 81 having a scale 88 adjacent the peripherythereof, the scale 88 beingmarked in degrees of I longitude. Arseconddisk 89.. of smallerdiameter than disk B'I-is provided with ascale 9 lmarked in. hours and minutesof theday... Disks. 81' and .89..

are rotatively joined together at: the axes thereof: 1

by'apin. or rivet .92. I In the operation of chart 85, the zero marking.

of scale 88 .is. brou ht by rotation .of one of the.

disks with respect to the other into, coincidence with themarking on scale. 9 I. indicative-of Green-1.- wic'h sun time as shown by the navigators; watch. By selecting the present. longitudezposietion. of. the-aircraft, on scale 88, local sungtirne will be d ed on scal mm d ate iacent the afore a d l itude po it on markin on scale 8 8.

In order to compensate for the cori'olis.force s encountered in, aircraft-which tend to tilt. the pendulously 'supported disk 54, a pair of diam. metrically opposed; supporting members,.93 and, 9.4,. asbest shown in 10 are securedto the.

-underside of disk, 56. by means of sqrewsjflfi, I

Notches 96 are formed: in the upper face ofeach of. the supports 93,.and 94.. to receive in adjusted position the hook portions 98 .of. each of. theweight members 91. respectively. Each of the. weight members 91 is provided with. a setfiscrew 99 by which the weight members are locked. in adjusted position. It is, apparent. that. with-a pair of adjusting weights, a large variety of fine. d ustments. are. pos ible. in order amore ccurately neutralize the. coriolis effect on the. pendulous assembly' In order to, compensate for phugoid, oscilla;- tionsv of the aircraft andassumingthat eachv oscillationhas .a period of one minute and it is.- desired to. take. an. average of. readings over a period of two minutes or two oscillations, ten readings of. thesun compass are taken. one. for eachtwelve seconds of elapsed time, each reading. being registered on an adding machine [0],- Fig, l. After the. ten readings have been registered. and. totaled, the average reading. is ob tainedby shifting the decimal point of the total one place to the left, thus giving a measure of relative bearing for the mid-point of the two minute interval. Although the time period of two phugoid oscillations is seconds, only 108 seconds elapse between the time at which the first reading is taken and the time the last reading is taken. This is because each reading rep resents an approximate average of the indicated relative bearing for the six seconds prior to and six seconds following the instant reading.

As best shown in Figs. 3 and 4, these figures being views of the sun compass in the same position as in Fig. l, the sun compass I2 is initially adjusted so that the outer gimbal axis thereof, is horizontal and at right angles to the centerline of the aircraft, the inner gimbal axis is horizontal and at right angles to the outer axis, and the rod 6| is vertical. The whole assembly in the spider is turned such that a line through 0 and on scale 83 is parallel with the centerline of the aircraft, the 0 being forward and the 180 being aft.

By reason Of this arrangement, the line 84 which represents the shadow of rod 6| of the sun compass, makes an angle 0 with respect to the heading of the aircraft. If the heading were true north, line 64 would make an'angle o with respect to the aircraft heading, this angle being time and latitude bein known.

the suns azimuth, as aforementioned. .The true heading of the aircraft, therefore, isgiven by the angle where r Angle may be determined, as aforementioned, by means of a computer such, for example, as the aforementioned azimuth computer, the sun Angle 0, of course, is the relative bearing of the aircraft with respect to the sun and is obtained by averaging the readings along spaced time intervals either of therecord of such readings kept by the navigator in the preferred form of the invention or of the photographic record of such readings in the alternative form thereof.

Angle 6 may be utilized in setting, up the third rectangularcoordinate system as set forth in my aforementioned copending application for Method. and Apparatus for Measuring the Earths Total Magnetic Field Vector.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. 7

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 1. Apparatus of the character disclosed for use in an aircraft during the flight thereof comprising, a transparent astral dome mounted in the top of said aircraft, a circular frame in said aircraft and having said astral dome attached thereto, a plurality of depending supports secured to said frame, a spider slideably mounted for vertical movement on said supports, locking means for securing said spider in adjusted position on said depending supports, a sun compass having a shadow producing rod and a dial therefor, said compass being supported by said spider, said spidermoving said sun compass into said astral dome when adjusted upwardly and moving said sun compass out of said dome when adjusted downwardly whereby the dial androd may be adjusted to receive the suns rays over a wide range of relative positions of the .sun and-aircraft.

2. Apparatus of the character disclosed for use in an aircraft in flight comprising, a transparent astral dome mounted in the top of said aircraft, a circular frame in said aircraft and having said astral dome attached thereto, a plurality of depending supports secured to said frame, each of said supports having a plurality of transverse bores therein, a spider having the extremities thereof slideably embracing said supports, retractible pins mounted in said extremities and adapted to extend through the bores in said supports thereby to lock said spider in selected adjusted positions, a sun compass mounted on said spider.

said. sun compass having a horizontal dial and a vertical rod for casting a shadow thereon, said sun compass moving in unison with said spider as said spider is moved to the selected adjusted positions whereby the sun compass receives the suns rays over a wide range of relative positions of the sun and aircraft.

ERICK O. SCHONSTEDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany May 16, 1948 

